The present invention relates to a folding unicycle that can be easily attached to a wheelchair solely by the wheelchair occupant while the occupant is seated in the wheelchair, thereby converting the wheelchair into a hand cranked tricycle.
Several prior art unicycle devices have been suggested for converting a wheelchair into a hand cranked tricycle. However, most of these devices are not foldable for easy transport and storage, and all have complicated means for attaching the unicycle to the wheelchair, which attachment means cannot be operated solely by a wheelchair occupant while seated in the wheelchair.
U.S. Pat. No. 3,485,510 describes a hand driven unicycle 20 for attachment to the front of a wheelchair 22 to form a tricycle. The attachment means includes a unicycle frame member 26 having a rear engagement end 28 attached to a bearing means 40 which is affixed to a transverse member 36 the ends of which are connected to a quick connect/disconnect means 32. The unicycle described in the ""510 patent cannot be folded, and attachment requires modification of the existing wheelchair, including removal of the front wheels, which cannot be easily done by a wheelchair user.
U.S. Pat. No. 4,316,616 describes a hand driven unicycle for attachment to the front of a wheelchair to form a tricycle. A generally rectangular rear framework formed by telescoping horizontal tube members 31, 32, 34, 35, 36 and 37 and vertical tube members 33 and 38 is removably attachable to the front frame portion of the wheelchair. An upper bar 49 and lower, telescoping bar 52, 53 attaches the rear framework to the sleeve 11 of the unicycle. A tension spring 57 is attached to the outer section of bar 53 and to the outer end of an L-shaped arm 59 secured to the lower end of steering post 9. Tension spring 57 automatically aligns the main wheel 12 in the central longitudinal plane of the wheelchair and attachment assembly when the crank arms 18 are released. The unicycle described in the ""616 patent cannot be folded and does not have an attachment means which can be easily operated by the wheelchair user.
U.S. Pat. No. 4,471,972 describes a foldable, hand driven unicycle 100 for attachment to the front of a wheelchair W to form a tricycle. The unicycle attachment means includes a frame 150 with attachment means 110 (FIG. 2) or 120 (FIGS. 7 and 8) for attaching the unicycle to the various frame members 61 of the frame W of a wheelchair. The attachment means 120 shown in FIGS. 7 and 8 (involving inserting frame member 55xe2x80x2 into a slot on the wheelchair engaging frame 120) which raises the castor wheels above the ground when locked into place. Frame members 52 and 55 of the unicycle can be folded upwardly from the position shown in FIGS. 1 and 2 to that shown in FIG. 3 for storage. The attachment means cannot be easily operated solely by a wheelchair user.
U.S. Pat. No. 4,483,548 describes a hand driven unicycle 10 for attachment to the front of a wheel chair to form a tricycle. A front tubular housing 50 has a mounting post 51 rotatable within housing 50. Mounting post 51 has a wheel 13 rotatably mounted thereon. Two rearwardly extending main posts 64 and 65 are fixedly attached at one of their ends to tubular housing 50. The other end of post 64 is fixedly attached to tube 29 of a frame attachable to the wheelchair, and the other end of post 65 is slidably received into tube 66 secured to tube 26 of the attachment frame. Post 65 is adjusted within tube 66 a distance to cause the small castor wheels 70 to be lifted off the ground. The unicycle of the ""548 patent is not foldable, and is not connectable to the wheelchair with attachment means that can be easily operated solely by the wheelchair user.
U.S. Pat. No. 4,720,117 describes a hand driven unicycle 10 for attachment to the front of a wheelchair 12 to form a tricycle by an attachment frame 14. The unicycle is not foldable and is connectable to the wheelchair by use of four separate attachment means which are difficult to manipulate solely by the wheelchair user.
The present invention relates to a foldable unicycle that is attachable to a wheelchair to form a hand driven tricycle. The unicycle has upper and lower drive train frames and means for attaching the unicycle to a wheelchair.
The means for attaching the unicycle to a wheelchair includes a positioning stand that holds the unicycle and its attachment means in a position adapted to receive a hitch means attached to the wheelchair frame. Latching means releasably latch together the attachment means and hitch means. The positioning stand of the unicycle and the front castor wheels of the wheelchair are lifted off the ground during latching of the unicycle attachment means to the hitch means of the wheelchair.
For easy transport and storage of the unicycle, folding means are provided for folding the upper drive train frame downwardly into a position adjacent the lower drive train frame. Folding means are also provided for folding the unicycle attachment means downwardly into a position adjacent the lower drive train frame.